Mucopolysaccharidosis III B (Sanfilippo type 13, MPS IIIB) is a lysosomal storage disorder due to the inherited deficiency of a-N-acetylglucosaminidase (NaGlu). The disease is characterized by mild somatic disease with severe neurological degeneration in most of patients by 6-10 years of age with rapid and progressive deterioration of social and adaptive abilities leading to premature death. No treatment is currently available for the central nervous system (CNS) disorder of MPS III B patients, which is usually the cause of premature death. Adeno-associated virus (AAV) has been shown to provide a promising gene delivery system for its ability of infecting wide range of tissues/organs and with no known pathogenesis in human. In this project, AAV-mediated gene therapy for the CNS disease of MPS III B is to be studied using a knock-out mouse model. Two AAV-vectors, containing human NaGlu cDNA driven by a CW promoter or the endogenous brain promoter, neuron specific enolase (NSE) promoter, have been constructed and have shown efficient expression of functional NaGlu and the correction of lysosomal storage by recombinant NaGlu in vitro in MPS IIIB cell cultures and in vivo in mouse brain. The vectors are to be delivered into multiple brain areas of MPS III B mice by direct microinjection, to study more efficient in vivo expression and distribution of rNaGlu and the correction of lysosomal storage in the brain after the injection. In addition, studies will be conducted to develop more efficient means of gene delivery into brain because limited distribution of gene therapy vectors in brain is one of the biggest obstacles for CNS therapies. It will be achieved by delivering AAV vectors containing an enhanced green fluorescent protein gene into multiple mouse brain areas by direct microinjection, to a) compare the distribution of gene expression mediated by different AAV serotype (1, 2 and 5) vectors; b) study the dispersion of gene expression delivered into mouse brain through different injection route, especially peripheral delivery; and c) study the spread of AAV vectors by modifying the delivery media of AAV viral vectors; d). Conduct multiple site infusion by a single injection, to increase the distribution of AAV vectors after a single injection. The goal of this project is to study the feasibility of using AAV-mediated gene therapy to treat the CNS disease in MPS III B children and to achieve broad distribution of AAV vectors in CNS, using mouse model. The long-term goal of this project is to develop novel therapy for CNS disease in MPS IIIB patients.